Our Radiation Environment

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  • All living organisms are exposed to a certain amount of natural background radiation .
  • The amount of this background radiation is based on many factors, including: the region of the country you live in, altitude, medical and dental procedures, and environmental variables.
  • On average, each citizen of the USA is exposed to approximately 300 mrem/year from these sources.
  • This exposure is in addition to any exposure you may receive as an occupational radiation worker.
  • Note that this is more than the exposure a medical radiation worker receives, and much more than a researcher receives.
  • The following pie chart breaks down the percentage each source contributes to your overall background exposure.

  • Radon: radon exposure occurs when radon gas is released from naturally occurring radioactive materials in the soil. The amount of radon exposure is found to be the highest wherever rocky granite is found.
  • Terrestrial: released from the soil.
  • Internal: released from naturally occurring material that our bodies need, such as potassium (K-40) and Carbon (C-14).
  • Cosmic: exposure from materials released by the sun and stars, or formed from interaction with cosmic rays in the atmosphere.
  • Consumer Products: includes items such as smoke detectors.
  • Other: includes fallout from nuclear weapons tests from the 1950's and 60's.


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